Abstract With more than five times the number of patients on the wait list than will receive a donor organ in the United States, the field of transplantation is facing a serious donor shortage crisis. The lack of available biomarkers for assessment of organ injury due to ischemia injury results in unnecessary waste of high quality organs. We aim to establish mitochondrial redox state, measured on the tissue surface with resonance Raman spectroscopy (RRS), as a biomarker for cold and warm ischemic injury in donor liver organs. We have previously demonstrated mitochondrial redox state, quantified as the resonance Raman reduced mitochondrial ratio (3RMR), as a marker of myocardial failure. In recent pilot work, we measured 3RMR from an ischemia liver and demonstrated a gradual increase during ischemia. In this project, we will optimize our prototype RRS system for liver measurements and build one dedicated to these studies. We will create an enhanced spectral library to allow accurate quantification of liver 3RMR by our regression algorithm. Finally, we will characterize our marker in a model of cold ischemia in rat donor livers. It is our hypothesis that 3RMR will predict the extent of ischemic damage and therefore the viability of the liver tissue on reperfusion. The availability of a real-time marker for ischemic damage would be transformative and would potentially increase the number of organs considered viable for transplant.